Zhu G.-P.,National Distant water Fisheries Engineering Research Center |
Zhu G.-P.,Shanghai Ocean University |
Zhu X.-Y.,Shanghai Ocean University |
Xia H.,Shanghai Ocean University |
And 3 more authors.
Chinese Journal of Ecology | Year: 2013
Based on the video records collected by the Chinese scientific observers of Antarctic krill fishery abroad the large-scale factory trawler "KAIXIN", which operated around the South Orkney Islands in the austral summer-autumn 2011 (March 6 to April 21, 2011), this paper analyzed the spatiotemporal distribution patterns of the Antarctic krill aggregations in the water areas of the Islands. The Antarctic krill aggregation were concentrated in the northwestern water areas of the Islands, and limited mostly at 60°00′S-60°15′S and 45°30′W-46°30′W. In different water layers, the aggregations were dominated in patched distribution. The percentage similarity index (PSI) analysis showed that there was a high similarity of 92. 3 between the 0-50 m and 50-100 m water layers. The scattered, patched, and belted aggregations had the highest proportion of occurrence in 0-50 m water layer, and the patched and belted aggregations had a very similar distribution pattern in different water layers (PSI =94. 4). The time segment with higher occurrence of Antarctic krill aggregations was from 1:00 to 18:00, and the occurrence decreased gradually to the lowest level from 19:00 to 20:00. This study could provide basic data for better understanding the formation mechanism of Antarctic krill fishing ground, and the operational references for exploiting Antarctic krill resources.
Zhu G.,Shanghai Ocean University |
Zhu G.,National Distant water Fisheries Engineering Research Center |
Zhang M.,Shanghai Ocean University |
Zhang M.,National Distant water Fisheries Engineering Research Center |
And 7 more authors.
Fisheries Research | Year: 2014
In severely depleted stocks, biological data taken prior to fishery decline are invaluable as a reference for recovery; and to understand the spatial population structure, especially when connectivity crosses management boundaries over the life history. Prior to a precipitous decline from 2010, Chilean jack mackerel (Trachurus murphyi) showed strong cyclic migrations hypothesized to encompass coastal areas regulated by national authorities along western South America and unregulated international waters offshore. In a preliminary analysis, we present data taken in international waters between 2000 and 2003 by a program sampling commercial catches from Chinese trawlers. Overall, catch length distributions occupied fork length classes from 240mm to 600mm, with a modal length class of 320mm for females and 340mm for males and the weight-length relationship was B W = 0.000 006 52FL3.0708. Males showed increasing predominance with length. Nearly 80% of fish had prey items in their stomachs; only 1% had full stomachs, suggesting that few fish were feeding intensively. However, mean fork length declined from 327mm to 259mm between 2000 and 2003, and population juvenescence as a result of exploitation may help explain these data. Nevertheless, adult spatial distributions were also consistent with migrations between feeding and spawning grounds. Distinguishing the spatial structure of such life history connectivity, and how it interacts with fishing activity, is critical to refining the conservation measures necessary to rebuild large oceanic fisheries and restore marine ecosystems. © 2013 Elsevier B.V.